Author Notes: It took a brilliant, adventurous chemist to discover the simplest way to make chocolate mousse at home. Hervé This, the father of molecular gastronomy, discovered how to make a flawless, creamy chocolate mousse out of just chocolate and water.

This all happens fast as the mixture cools, so chances are you'll go too far on your first try. Don't worry — just return it to the pan, melt it, and start over (see step 3). Once you have the rhythm down, you can flavor it as you wish with liqueurs or coffee or spices, sweeten it to your liking, or just keep it dark and intense. In all of these scenarios, a little whipped cream up top is never a bad idea. Adapted from Molecular Gastronomy: Exploring the Science of Flavor (Columbia University Press, 2008) —Genius Recipes

Simply pour water into a saucepan (which will be improved from the gastronomic point of view if it is flavored with orange juice, for example, or cassis puree). Then, over medium-low heat, whisk in the chocolate. The result is a homogenous sauce.

Put the saucepan in a bowl partly filled with ice cubes (or pour into another bowl over the ice -- it will chill faster), then whisk the chocolate sauce, either manually with a whisk or with an electric mixer (if using an electric mixer, watch closely -- it will thicken faster). Whisking creates large air bubbles in the sauce, which steadily thickens. After a while strands of chocolate form inside the loops of the whisk. Pour or spoon immediately into ramekins, small bowls or jars and let set.

Note: Three things can go wrong. Here's how to fix them. If your chocolate doesn't contain enough fat, melt the mixture again, add some chocolate, and then whisk it again. If the mousse is not light enough, melt the mixture again, add some water, and whisk it once more. If you whisk it too much, so that it becomes grainy, this means that the foam has turned into an emulsion. In that case simply melt the mixture and whisk it again, adding nothing.

I had terrible difficulty getting the consistency correct (even after trying the fixes described in the recipe). After three failed attempts with high quality chocolate, I will be returning to more complicated recipes that produce a more consistent result. Was really hoping that this would be a wonderful, easy mousse!

I've been making chocolate mousse this way for almost 20 years, except I use cream in place of the water which makes a ganache. When the ganache is whipped, it turns into mousse. Very handy for filling and frosting a layer cake. I divide it into 2 parts. Leave one part as is for frosting, and whip the other part for filling. It's also great piped into hollowed out orange halves or onto strawberry halves, made into sandwich cookies (which are good as is and even better when eaten frozen!), made into a pie, or just served in a little dish with whipped cream and maybe a few chocolate shavings.

I really like the idea of this recipe made with water because it contains a lot less fat without the cream, and I won't eat or serve anything that has raw eggs in it, as traditional mousse does. Can't wait to try this! I think I may make some fudgsicles out of it.

Inexplicably this just works! I'm in awe - and it was so easy! Great result too. Texture is very dense, a little like mudcake, but mousse instead. Flavour is intensely chocolatey - best chocolate flavour I've ever had in a mousse and it's delightfully not very sweet, so the chocolate flavour shines. Best of all, it's easy to make just before you need it without having planned ahead.

It has to do with the quantity of water. If you were to add just a small amount, the chocolate would seize up and turn into a thick, sludgy mess. For some reason, adding a larger amount of water or (other liquid) prevents this and will actually mix with it.

Not sure what i did wrong. Perhaps I didn't have enough fat or didn't whisk long enough. But after refrigerating ours turned out quite thick. My girlfriend described it as "fudgy". We still thought it was yummy and devoured them.

So easy! and it takes just a few moments of whisking for the chocolate to begin setting. I flavored it with a few drops of orange essential oil and will serve it with lightly sweetened whipped cream. My house was pretty warm today and the mousse began to "unsettle" after a few moments in the ramekins, so next time I'll prechill the containers and get them into the refrigerator more quickly. Pity the poor person who has to lick the bowl, the beaters, the spatula, her fingers...

My one issue, though, is that I often end up with mousse that tastes too fruity. You must use high-quality chocolate, but it takes a bit of luck and careful consideration to find the best one for this mousse... I think one that has more "creamy" and "coffee" notes, without any sharp angles in the flavor. Honestly, one of the best ones I've found is the Trader Joe's Pound Plus dark chocolate because it seems to have a very smooth, "chocolatey" flavor.